1. Technical Field
The embodiments described herein relate to microelectronics, and more particularly, to an adjustable signal generating device and related method for generating the adjustable signal.
2. Related Art
FIG. 1 is a schematic diagram showing a superheterodyne receiver under the existing technologies. The superheterodyne receive may include the following: an input circuit 100, a high-frequency amplifier 101, a mixer 102, a local oscillator 103, an intermediate frequency amplifier 104, an amplitude limiter 105, a frequency discriminator 106, a low frequency amplifier 107. In the superheterodyne receiver, because different channels corresponds to different receiving frequencies, the local oscillator 103 needs to be adjusted to generate different oscillation frequencies. FIG. 2 is a circuit diagram showing a local oscillator under the existing technologies. The LC oscillator is usually used for the local oscillator and the LC oscillator includes a capacitor 20 and an inductor 21, the capacitor 20 includes a variable capacitor 201 and a fixed capacitor 202. The user may change the capacitance of the variable capacitor 201 by turning the knob continuously, thus changing the local oscillator frequency of the local oscillator. Because the nature is an analog world, a continuous adjustment method would make the user experience much better.
However, these aforementioned analog regulation method relies mainly on the absolute value of the variable capacitor 201 to determine the oscillation frequency, in the production process, there is a need to fine tune the absolute value of the variable capacitor 201 manually, making the absolute frequency accuracy of generated local oscillator signal low. The problem of low accuracy for signals generated under continuous adjustment method also exists in some other adjustable signal circuits including an amplitude adjustment circuit.